1. Field of the Invention
This invention is in the field of distributed digital process control systems and, more particularly, relates to a plantwide system for monitoring and controlling industrial and electric utility plants, including intersystem communications and related plant management functions for plants ranging from modest to very large.
2. Description of the Prior Art
Digital process control and data acquisition systems such as that identified as the TDC 2000 process control system manufactured and sold by Honeywell Inc.'s Process Management Systems Division, for example, include a comprehensive set of algorithms and auxiliaries to control and monitor various manufacturing processes or the operation of utilities. The TDC 2000 Control System can be tailored to satisfy a wide range of process requirements at the loop or unit level. The TDC 2000 system includes standardized units that are linked together by a data highway, or common communication medium or bus, and each of the major units of such a system includes a microprocessor with its own firmware and data base to provide a distributed control system. Such distributed digital data acquisition and control systems to date have been essentially limited to controlling part of the processes conducted in petroleum refineries, for example, such as catalytic crackers, or in an electric utility plant the operation of boilers, generators, nuclear reactors, etc.
There is a need for a wider span, or degree, of control to permit plant-wide control of all the processes conducted by a given facility to improve efficiency and the products produced by large, complex industrial and utility facilities. Typically, attempts to do this, as taught by the prior art, have required large general-purpose, or large specialized, digital data-processing systems to provide a greater degree of control and information gathering capability over one or more control systems, such as that provided by the TDC 2000 Control System, hereinafter sometimes referred to as a process control subsystem, that do the actual controlling of processes or portions of processes performed. Typically, the analysis and special management functions needed to optimize processes, throughput, quality, to control inventory, etc., have been performed by data-processing systems that do not communicate directly, on a real-time basis, with process control subsystems as defined above. Thus, there exists a need for a higher level plant management system that can gather data on the operation of a total plant by continuously monitoring the performance of the various process control subsystems of the plant to provide plantwide control on a real-time basis.
One of the requirements of such a plant management system is for a high-performance universal operator station at which one or more operators can supervise and control the processes being executed by the plant, or the total operation of a large plant from raw material input to finished goods output. Such a system must also be reliable, fault tolerant, and preferably be sufficiently modular so that additional functions can be added as needed to tailor a plant management system to meet the specific requirements of any given manufacturing complex at a minimum of cost while at the same time providing a highly reliable system which can be readily modified to meet changing requirements placed on such a complex.